Formation conditions and exploration potential of tight oil in the Permian saline lacustrine dolomitic rock, Junggar Basin, NW China

Abstract

The features and exploration potential of the Permian tight oil in the Junggar Basin were analyzed and evaluated using outcrop, core and geochemical data etc. The Junggar Basin in the Early-Mid Permian is a saline lacustrine basin after the residual sea is closed, a set of hybrid sedimentation of deep-lake dark mudstone and dolomitic rock is developed, and the high-quality mudstone source rocks and the dolomite mudstone are alternated. High quality source rocks in mature stage are next to tight dolomitic rock reservoirs closely and provide good conditions for tight oil accumulation of proximal source type. Tight oil reservoirs are mainly distributed in the centre and slope region of the lake basin, and two types sweetspots of “dissolved pore” and “fracture-pore” exist locally. The enrichment of tight oil is controlled by the distribution of effective source rocks and dolomitic rocks, and the tight oil occurs in the entire strata vertically and spreads across large continuous areas horizontally. The Junggar Basin has four Permian tight oil distribution areas, Fencheng Formation in the Mahu sag, Lucaogou Formation in the Jimusaer sag, Pidiquan Formation in the Shazhang-Shishugou sag, and Lucaogou Formation in the Bogeda piedmont. A number of wells obtained oil flow in these areas, suggesting great resource potential and favorable targets for future exploration. Key words: Junggar Basin, Permian, saltwater lake, dolomitic rock, tight oil, resource potential